Flu Shot Prevents Heart Attacks and Stroke

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Having a flu shot can dramatically reduce the risk of heart attacks and stroke both for people with and without underlying conditions such as heart disease, according to data from two sets of research presented at the 2012 Canadian Cardiovascular Congress.

A team of researchers at Women’s College Hospital and the University of Toronto looked at published clinical studies dating back to the 1960s, which included over 3,000 people with and without established heart disease. Their analysis showed that individuals who received a flu shot had a 50% lower risk of a major cardiac event—including heart attack, stroke, or cardiac death—compared with those who received placebo, after a year of follow-up. In fact, the flu vaccine appeared to reduce death from any cause by about 40%.

A separate set of studies, by a team at Sunnybrook Health Sciences Centre, showed that, over the course of a flu season, people with implantable cardiac defibrillators (ICDs) who have a flu vaccination receive fewer shocks from their devices than those who haven’t been vaccinated. An ICD is designed to detect cardiac arrhythmia in a patient and correct it by delivering an electric jolt to the heart. Interestingly, anecdotal evidence suggests that patients receive more ICD shocks during the flu season, explain cardiologists Ramanan Kumareswaran, M.D., and Sheldon Singh, M.D. “We were trying to figure out what we can do to reduce the amount of shocks in (our clinic’s) ICD population during the flu season.”

The researchers asked 230 of their ICD patients to complete a survey that included health status and whether they had received a flu shot in the past year. The average age of the patient was 70–74 years. When the investigators reviewed the data they found that respondents who hadn’t been given a flu shot received more ICD shocks than those who had been vaccinated. More specifically, 10.6% of flu vaccinated patients received at least one ICD therapy, compared with 13.7% of the nonvaccinated patients.

“What is interesting is that if this is consistent over time, it could be of significant benefit to our patient population who already have compromised survival to start with,” Dr. Singh states. “We would like to look at this on a larger scale to determine whether or not our results can be replicated.”

The Women’s College Hospital and University of Toronto team likewise wants to see larger studies to verify their data suggesting that flu vaccination reduces the risk of heart attacks and stroke. “A large study that was international in scope and representative of patients such as those in North America and Canada in particular could help answer this question,” states cardiology Jacob Udell, who presented the data at the Canadian Cardiovascular Congress.

Dr. Udell believes flu vaccination is far underused, and says the latest findings support current guideline recommendations for flu vaccination among individuals who’ve already suffered a heart attack, but not just for reducing flu risk. A dedicated large-scale study could show that flu vaccination reduces fatal cardiac events, he suggests. “The use of the vaccine is still much too low, less than 50% of the general population; its even poorly used among health care workers. Imagine if this vaccine could also be a proven way to prevent heart disease.”